Biology 9700 · AS & A Level · Natural and artificial selection
Natural and artificial selection — practice question
The wolf, Canis lupus, is found in North America. Wolves can have either a grey coat or a black coat. The coat colour of a particular wolf is determined by the DNA it inherits at the CPD103 gene locus. Each wolf inherits two copies of CPD103, one from each parent. A wolf that inherits one copy of the black version of the CPD103 gene has a black coat. Besides giving black coat colour, the protein encoded by the CPD103 gene also protects against infectious lung disease. Canine distemper virus (CDV) causes severe lung disease in wolves. Wolves that were infected by CDV in the past have antibodies against CDV (anti-CDV antibodies) in their blood.
(a)[3]
State the term used to describe: an organism with two copies of each gene; a form of a gene; a form of a gene that produces a phenotypic effect in a heterozygote.
(b)[4]
CDV can be transmitted from domestic dogs to wolves. Explain how natural selection brings about this pattern in the distribution of black wolves.
(c)[4]
Fig. 4.1 shows the link between the percentage of wolves in a population with anti-CDV antibodies in their blood and the percentage of wolves in that population that are black. The line of best fit was drawn after comparing the different wolf populations. With reference to Fig. 4.1, state the relationship between the percentage of wolves with anti-CDV antibodies and wolf coat colour, and suggest reasons for this relationship.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “diploid” …